Optogenetics is an established technique that uses visible light to modulate membrane voltage in neural cells. The visible light can be used to trigger changes in proteins that modulate membrane potentials in neuronal cells through excitatory or inhibitory membrane currents. This ability to modulate neuronal cells has proven instrumental in preclinical studies and holds enormous potential for the treatment of diseases such as Parkinson's, epilepsy, and depression. However, current techniques used for optogenetic control are too invasive for clinical applications. That is, although optogenetics allows researchers to study parts of the brain like never before, it is limited because it is invasive, and visible light cannot travel very deeply into tissue.